This application claims the priority of Korean Patent Application No. 10-2003-0043520 filed on Jun. 30, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of Invention
Apparatuses and methods consistent with the present invention relate to time synchronization between multimedia content and segment metadata for multimedia content, and more particularly, to a system and method for synchronizing content and segment metadata received via different transmission channels using predetermined time information.
2. Description of the Related Art
As digital broadcasting services have become widely distributed, technical development for an effective application using multimedia contents (in the present invention, the various types of contents mentioned below are all regarded as multimedia contents) is highly required. For example, there is provided a personal video recorder (PVR) application, which provides a time shifting function for content broadcasted in real time by storing the broadcast contents therein. PVR may be a good example of a change in the way of viewing TV, in that it allows useful functions such as automatic commercial advance, instant replay, pause and trick play, which can be realized only in recording media such as video tapes and DVDs, to be applied to TV programs being broadcast in real time. The PVR application can have more powerful functions and provide users with more convenient functions, since it uses additional information, i.e. metadata, for broadcast contents. In particular, since segment metadata (in the present invention, metadata mentioned below are all regarded as segment metadata) is able to provide additional information such as highlights, tables of contents and bookmarks for the contents, users can view the broadcast contents in a desired, non-linear manner. For example, it is possible for users to view collected highlights of scoring scenes in a soccer game, to move and view again a desired second half of the third inning while viewing a first half of the seventh inning in a baseball game, to view only a desired news segment corresponding to a specific field in a news program, to firstly view desired songs of a specific singer in a show program, or the like. As mentioned above, a next generation PVR using segment metadata can provide users with a content segment browser which is a more convenient and powerful broadcast viewing tool.
As a representative standard for segment metadata, there is provided the “TV-Anytime Metadata” standard specified in the TV-Anytime Forum. This metadata standard expressed in an XML format defines the metadata for a segment and a segment group. FIG. 1A shows an example of metadata in which a segment is described. A segment is a unit representing a portion of contents, in which information such as segment ID, relevant broadcast program ID, descriptor for the segment, e.g. title/synopsis/keyword, and temporal positions of the segment and a key frame.
FIG. 1B shows an example of metadata in which a segment group is described. The segment group is a unit for grouping one or more segments from one or several broadcast programs. Group types for use in segment grouping are classified into highlights, highlights/objects, highlights/events, bookmarks, bookmarks/objects, bookmarks/events, themeGroup, preview, preview/title, preview/slideshow, tableOfContents, synopsis, shots, insertionPoints, alternativeGroups, other, and the like. If the group comprises only a group ID and the segment for one broadcast program other than the aforementioned group types, the metadata for the segment group defines information including a relevant broadcast program ID, a group descriptor such as title/synopsis/keyword, a group interval, a key frame position, IDs of segments belonging to the group, and the like.
A time point of each segment in segment metadata of TV-Anytime is described as a relative time point with respect to a start time point of the contents. Therefore, a reference time point to which the segment refers should be additionally described in the metadata. FIG. 1C shows an example of the metadata for representing such a reference time point.
At this time, if the aforementioned metadata are not provided simultaneously via the same transmission channel as that for the contents but provided via a different transmission channel by a content provider or another metadata provider, a time difference may be produced at the receiving device upon reception of the contents and metadata. Accordingly, a time synchronization process is required.